FIG. 7 is a configurational drawing of a plasma CVD system according to a conventional technology. As shown in the drawing, a chamber 2, which is a cylindrical vacuum container made of aluminum, is provided on a base 1, and a film deposition room 3 is defined within the chamber 2. A disk-shaped ceiling board 4, which is an electromagnetic wave transmission window, is provided above the film deposition room 3. A susceptor 5, which is a support stand for a wafer 6, is disposed within the film deposition room 3. The susceptor 5 is a disk-shaped member for bearing the wafer 6, is composed of a ceramic material such as Al2O3 or AlN, and is supported by a support shaft 8. A heater 6a, which is a heating means for keeping the wafer 6 at a predetermined temperature, and a coolant passage 6b for allowing a coolant as cooling means to pass therethrough are buried within the susceptor 5. An electrostatic chuck electrode 7 for an electrostatic chuck, which electrostatically attracts and holds the wafer 6, is also buried within the susceptor 5. A predetermined direct current voltage, which is an output voltage from a direct current power source 13, is applied to the electrostatic chuck electrode 7 via a low pass filter 12. Coulomb force based on a potential difference between the wafer 6 and the electrostatic chuck electrode 7, which occurs because of the application of the DC voltage, results in the attraction of the wafer 6 to the surface of the susceptor 5.
A bias high frequency power source 11 is connected to the electrostatic chuck electrode 7 in the plasma CVD system via a matching instrument 10 for performing impedance matching and a capacitor 9. That is, the electrostatic chuck electrode 7 also functions as a bias electrode. The aforementioned LPF 12 functions as a filter for cutting off an alternating current portion of the bias high frequency power source 11.
As described above, a bias voltage is applied to the wafer 6 via the electrostatic chuck electrode 7 by supplying a high frequency power from the bias high frequency power source 11. The bias voltage is a so-called RF bias. A direct current negative voltage, generated by application of the RF bias, accelerates ions in a plasma to strike the face of the wafer 6 exposed to a plasma atmosphere, whereby various effects, such as promotion of a surface reaction, anisotropic etching, and improvement in film quality, can be obtained.
An exhaust port 15 is provided in the base 1, and gases within the film deposition room 3 are discharged to a vacuum pumping system (not shown) via the exhaust port 15 to bring the interior of the film deposition room 3 to a low pressure environment. Various gases for performing film deposition are supplied to the interior of the film deposition room 3 in this low pressure environment via nozzles (not shown). To form a film of silicon nitride (SiN) on the wafer 6, for example, SiH4, for example, is supplied as a source gas, and NH3 or N2, for example, is supplied as a nitriding gas.
A power supply antenna 16 in a spiral form is mounted on the upper surface of the ceiling board 4. A plasma generation high frequency power source 18 is connected to the power supply antenna 16 via a matching instrument 17 for performing impedance matching. High frequency power is supplied from the plasma generation high frequency power source 18 to the power supply antenna 16, whereby electromagnetic waves 19 are thrown from the power supply antenna 16 into the film deposition room 3 through the ceiling board 4. Various gases supplied into the film deposition room 3 are converted to a plasma state by the energy (high frequency power) of the electromagnetic waves 19. This plasma is utilized to carry out processing, such as deposition of a predetermined metal film on the wafer 6.
In the above-described plasma CVD system, in order to ensure the predetermined performance of the plasma CVD system under constant plasma conditions, defined by the types, pressures and flow rates of the gases for plasma formation, and the power (electric power) supplied to the power supply antenna 16, it is necessary to measure the potential of the wafer 6 under predetermined plasma conditions. If, under these plasma conditions, the potential of the wafer 6 is a constant potential, it can be ensured that the quality, etc. of the outcome of plasma processing, such as a deposited film, is constant; namely, reproducibility can be ensured.
However, it is difficult to measure the potential of the wafer 6 during plasma processing without causing a problem. The potential can be measured easily if a probe of a measuring device can be brought into contact with the wafer 6. However, the contact of the probe results in metal contamination of the wafer 6, deteriorating the characteristics of the wafer 6 as a product. That is, to measure the potential of the wafer 6 during plasma processing without any problem, measurement needs to be made in a noncontact manner.
The present invention has been accomplished in the light of the above-described earlier technology. It is an object of the invention to provide a wafer potential measuring method and apparatus, which can measure the potential of a wafer in a noncontact manner, i.e., without contact of a probe or the like with the wafer, and a plasma processing system having the wafer potential measuring apparatus.
In the above plasma CVD system, moreover, it may be desired to control the temperature of the wafer 6. During a burying process for burying a predetermined metal in a very thin trench, for example, a high efficiency is obtained if the burying is performed in an atmosphere where an etching action by ions of the metal is predominant. Thus, the wafer is desired to be kept at a predetermined high temperature. To avoid damage due to strikes of metal ions against an element already formed on the wafer 6, on the other hand, the burying needs to be performed in an atmosphere where an etching action by the metal ions is suppressed. Thus, the wafer is desired to be kept at a predetermined low temperature.
In short, even when plasma conditions, defined by the types, pressures and flow rates of the gases for plasma formation, and the power (electric power) supplied to the power supply antenna 16, are set to be constant, the outcome of plasma processing, such as the quality of a deposited film, is different, depending on the temperature of the wafer 6. Thus, the temperature of the wafer 6 needs to be managed in order to ensure the reproducibility of plasma processing.
Nevertheless, an appropriate method for detection of the wafer temperature, which can exercise temperature control conveniently and precisely, has not been existent.
In view of the aforementioned earlier technology, the present invention has, as another object, the provision of a wafer temperature detecting method and apparatus capable of exercising the temperature control of a wafer conveniently and precisely.